Github user liurenjie1024 commented on the issue:
https://github.com/apache/flink/pull/5688
@xccui Thanks for you suggestions.
1. Add an it test for this is difficult. Think about it, I need to ensure
that elements to be processed while keeping the job running, and it's difficult
to achieve this. But I will do some manual test for that.
2. I'll add doc for that.
3. I'll squash the commits when review is done.---
